The present invention relates to a method and apparatus for the continuous gasification of solid fuel. More particularly, the present invention relates to a method and apparatus for continuous gasification of solid fuel having a high water content, such as biomass or raw brown coal, in a countercurrent. Such fuel having a high water content is dried, heated, and ultimately gasified in a glowing fuel bed. Steam liberated from the fuel during the drying thereof is reduced at the glowing fuel bed during gasification of the fuel, with hot generator gas thereby being formed during the gasification. The thus-formed hot generator gas is supplied to a user, e.g. in the form of hot gas itself.
It has been known to gasify fuel and utilize, at the same time, the steam liberated during the drying of such fuel as gasification medium, to obtain generator gas. Generator gas contains condensable matter, and for this reason such generator gas is either combusted, uncooled, or purified by cleaning prior to combustion thereof, during which a loss of heat occurs. The condensable components are combustible (phenols, tar), and, in part, non-combustible (steam).
In order to increase the calorific value of the generator gas, it has been known to dry the fuel, prior to gasification thereof, with a portion of the hot generator gas so formed during gasification, and also to utilize the water content of the generator gas by injecting the fuel into the glowing fuel bed. However, part of the generator gas is lost during this process, since this portion of the generator gas is subjected to chemical change when passing through the glowing fuel bed.